This invention deals generally with a blender for solid particulate matter, and more specifically with a blender of the type which is a cylindrical vessel with a central lift column or pipe through which a gas is pumped to move material from the bottom to the top of the vessel for mixing.
Mineral feed to crushing equipment varies in chemical composition and in other critical properties such that there is a need for homogenizing the feeds to the downstream process. This is typically done by utilizing a blender means such as a particulate blender intermediate the crushing equipment and the downstream process.
Particulate blenders which are cylindrical vessels with a central lift pipe or column to raise inventory from the bottom of the blender to the top for mixing are well known in the art. They are available in versions which feed the new material into the vessel at either the bottom or the top of the vessel, and both types use a gas pumped up through the central pipe to lift material from the bottom to the top, which material is then moved by gravity to the bottom again through various deflector structures, which in certain prior art blenders consist generally of narrow flow passages which cause the material to be mixed.
Such blenders are used to primarily blend free flowing granular materials both in the batch and continuous mode. When non-free flowing materials such as certain powders are used, however, the customarily narrow internal blending passageways, tubes or channels can tend to become blocked and rendered ineffective. It would be desirable, therefore, to have a design which can function on non-free flowing materials in a blending mode with a high degree of energy efficiency.
In addition, in mineral processing applications equipment downstream of the blender, typically pyroprocessing equipment, will run at a higher level of availability than the mineral processing equipment, i.e., the crushers and mills, that are located upstream of the blender. Consequently, the designed throughput of "upstream" equipment must be considerably higher than that of "downstream" equipment. Therefore, there is a need to utilize, in conjunction with the blending equipment, a raw feed storage means in order to ensure a steady flow of material through the blender and thereafter to pyroprocessing equipment during those times when mineral processing equipment is not available. It would be desirable, therefore, to have a blending device that operates in conjunction with a feed storage means in an efficient manner.
These objectives are realized by providing a blender in which the internal volume is compartmentalized with large flow passage areas for the non-free flowing materials which are also designed to create differences in velocity and mixing as material passes through the blender. The blender of this invention is also adaptable to store and to internally recycle blender inventory in a manner such that the net flow to the subsequent downstream process can be controlled at a predetermined rate thereby integrating process feed with the blending function and, in addition, providing a means to control the process feed rate.